May 20, 2013 2000 UTC Day 1 Convective Outlook
Updated: Mon May 20 20:01:39 UTC 2013
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the southern plains and ozark plateau this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20130520 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20130520 2000 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Probabilistic Damaging Wind Graphic
20130520 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Probabilistic Large Hail Graphic
20130520 2000 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 71,461 5,030,454 Oklahoma City, OK...Tulsa, OK...Springfield, MO...Norman, OK...Broken Arrow, OK...
SLIGHT 417,472 56,858,906 Chicago, IL...Dallas, TX...Indianapolis, IN...Ft. Worth, TX...Detroit, MI...
   SPC AC 201957
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0257 PM CDT MON MAY 20 2013
   
   VALID 202000Z - 211200Z
   
   ...THERE IS A MDT RISK OF SVR TSTMS OVER NORTH CENTRAL
   TX...CENTRAL/ERN OK...EXTREME SERN KS...SRN MO...AND NWRN AR...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLAINS INTO THE
   GREAT LAKES REGION...
   
   ...SRN PLAINS INTO THE OZARKS...
   MINOR ADJUSTMENTS HAVE BEEN MADE TO THE OUTLOOK BASED ON CURRENT
   BOUNDARY LOCATIONS AND RECENT CONVECTIVE INITIATION.
   
   SEVERE STORMS HAVE DEVELOPED ALONG THE DRY LINE FROM THE WRN PART OF
   NORTH TEXAS INTO CENTRAL OK...WITH ADDITIONAL STORMS OVER SERN KS
   AND SWRN MO.  SPECIAL SOUNDINGS AT 17-18Z FROM OUN/SGF/FWD INDICATE
   STEEP LAPSE RATES ARE PERSISTING ABOVE 850 MB THAT ARE ASSOCIATED
   WITH THE ELEVATED MIXED LAYER ACROSS THE REGION.  WITH SURFACE
   DEWPOINTS IN THE UPPER 60S/LOWER 70S AND TEMPERATURES WARMING INTO
   THE LOW/MID 80S IN OK AND NEAR 90 IN NRN TX...A VERY UNSTABLE
   ENVIRONMENT IS PRESENT WITH SBCAPE RANGING FROM 3500-5000 J/KG. DEEP
   LAYER SHEAR OF 40-50 KT WILL ENHANCE STORM ORGANIZATION AND
   INTENSITY WITH POTENTIAL FOR SUPERCELLS AND BOWING LINE SEGMENTS. 
   VERY LARGE HAIL...DAMAGING WIND AND SEVERAL STRONG TORNADOES WILL BE
   POSSIBLE THROUGH THE EVENING AS ACTIVITY CONTINUES TO DEVELOP AND
   SPREAD EWD/NEWD.
   
   ...GA/FL...
   STRONGER STORMS APPEAR MOST LIKELY FROM SRN GA AND NRN FL INTO THE
   SWRN PART OF THE FL PENINSULA...IN ASSOCIATION WITH AN UPPER LOW
   OVER SRN GA/NRN FL.  ISOLATED MARGINAL HAIL AND WET MICROBURSTS MAY
   ACCOMPANY A FEW OF THE CELLS BUT OVERALL SEVERE THREAT SHOULD BE
   LIMITED.
   
   ..WEISS.. 05/20/2013
   
   .PREV DISCUSSION... /ISSUED 1130 AM CDT MON MAY 20 2013/
   
   ...SRN PLAINS TO OZARK PLATEAU...
   OVERALL FORECAST SCENARIO REMAINS SIMILAR TO EARLIER OUTLOOKS WITH
   ONLY MINOR OVERALL CHANGES TO INDIVIDUAL HAZARD PROBABILITIES.
   MID-LEVEL SPEED MAX /65 KT AT 500 MB IN THE 12Z ABQ RAOB/ ATTENDANT
   TO THE SHORTWAVE IMPULSE OVER THE LEE OF THE SRN ROCKIES WILL
   OVERSPREAD MOST OF OK TO THE LOWER MO VALLEY BY EARLY EVENING.
   TRAILING PORTION OF COLD FRONT HAS BECOME SLOW-MOVING FROM SERN KS
   TO SWRN OK...INTERSECTING A DRYLINE THAT WILL BECOME WELL
   ESTABLISHED S/SWWD ACROSS THE TX BIG COUNTRY TO THE ERN EDWARDS
   PLATEAU BY LATE AFTERNOON. SCATTERED TSTMS WILL INITIATE ALONG THESE
   BOUNDARIES BY MID-AFTERNOON. MORNING CONVECTION-ALLOWING MODEL
   GUIDANCE ARE INSISTENT THAT THIS ACTIVITY WILL RAPIDLY GROW UPSCALE
   INTO NUMEROUS LINE SEGMENTS...SURGING EWD THIS EVENING WITHIN A
   STRONGLY UNSTABLE ENVIRONMENT.
   
   INITIAL TSTMS WILL BECOME SUPERCELLUAR QUICKLY WITH VERY LARGE HAIL
   LIKELY AS HODOGRAPHS/INSTABILITY WILL BE QUITE FAVORABLE...ALONG
   WITH A FEW TORNADOES. THE GREATEST RISK FOR A COUPLE OF STRONG
   TORNADOES SHOULD EXIST FROM S-CNTRL INTO E-CNTRL OK. BUT WITH
   PREDOMINANT SWLY COMPONENT TO LOW-LEVEL FLOW AND MODERATE 0-1 KM
   SHEAR...OVERALL TORNADO INTENSITY/LONGEVITY MAY BE
   TEMPERED...ESPECIALLY WITH CONVECTION EXPECTED TO GROW UPSCALE SO
   QUICKLY. NEVERTHELESS...THIS GROWTH SHOULD YIELD BOWING LINEAR
   SEGMENTS CAPABLE OF SWATHS OF WIDESPREAD DAMAGING WINDS...LARGE HAIL
   AND A FEW TORNADOES.
   
   ...MID/UPPER-MS VALLEY TO CNTRL GREAT LAKES...
   PRIMARY CHANGE HAS BEEN TO EXPAND DAMAGING WIND PROBABILITIES E/NEWD
   FOR THIS AFTERNOON AND EVENING. IN THE WAKE OF CONVECTION
   YESTERDAY...LOW-LEVEL MOISTURE PLUME HAS BECOME CONFINED FROM LOWER
   MI S/SSWD TO THE CONFLUENCE OF THE MS/OH RIVERS. BUT PLENTIFUL
   HEATING IS OCCURRING TO THE N OF THIS PLUME WILL YIELD A RECOVERING
   AIR MASS DOWNSTREAM OF A TSTM CLUSTER APPROACHING CNTRL MO. THIS
   ACTIVITY SHOULD GROW UPSCALE ALONG THE EDGE OF THE INSTABILITY
   AXIS...WITH ADDITIONAL LINEAR SEGMENTS EMANATING E/NEWD FROM THE
   OZARK PLATEAU LATER TODAY. SWATHS OF DAMAGING WINDS...LARGE HAIL AND
   A COUPLE OF TORNADOES WILL BE POSSIBLE.
   
   FARTHER N/NW...SCATTERED TSTMS ARE EXPECTED TO FORM OVER LOWER MI
   AND IN PARTS OF THE UPPER MIDWEST IN ASSOCIATION WITH AN UPPER-LEVEL
   LOW CENTERED OVER ERN SD. BUOYANCY WILL BE STRONGEST OVER LOWER MI
   WITHIN THE LOW-LEVEL MOISTURE PLUME CHARACTERIZED BY MIDDLE TO UPPER
   60S SURFACE DEW POINTS. IN THE UPPER MIDWEST...POCKETS OF ROBUST
   SURFACE HEATING WILL SUPPORT AT LEAST MODEST INSTABILITY AND WITH
   STRONG UNIDIRECTIONAL WIND PROFILES...SETUP COULD A FEW ORGANIZED
   TSTM CLUSTERS. A MIX OF ISOLATED SEVERE HAIL/WIND SHOULD BE THE
   PRIMARY THREATS.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z